As miniaturization of electronic apparatuses has advanced recently, miniaturization has been increasingly required in semiconductor devices used in the electronic apparatuses. For example, in conventional optical devices, an optical element is housed in a recessed package, and protective glass or the like (hereinafter referred to as a transparent member) is used to seal the opening of the recessed package. The conventional optical devices are miniaturized by reducing the bonding width of the transparent member, the distance from the external edge of the transparent member to the external edge of the package, and the width of each side wall portion (hereinafter referred to as a rib) of the recessed shape. In contrast to this structure, there are disclosed optical devices having a structure in which a transparent member is secured directly onto an optical element and housed in a recessed package for further miniaturization.
Thus, the conventional optical devices are miniaturized by housing the optical element in the recessed package and reducing the bonding width of the transparent member, the distance from the external edge of the transparent member to the external edge of the package, and the rib width of the recessed shape, or by securing the transparent member directly onto the optical element and housing the resulting structure in the recessed package with the reduced rib. In these optical devices, when the element is mounted on the substrate, back terminals formed on the back surface of the package are joined to respective terminals on the substrate. However, only the junction between the back terminals and the substrate may fail to offer a sufficient mounting strength. Thus, side terminals extended from the respective back terminals may be provided on each side of the package. Then, the device may be mounted in the package by soldering such that solder filets are formed on the respective side terminals. Even in this case, disadvantageously, the conventional side terminals are not high enough, preventing the formation of solder filets large enough to ensure a sufficient, reliable mounting strength.
For example, if ceramic layers each having an internal wiring layer are laminated together to form a recessed package, through-via are formed to electrically connect wires between the laminates. The mounting strength may be affected by the reduced distance between each of the through-via and a corresponding penetrating portion (hereinafter referred to as a castellation) forming the side terminal. Thus, to ensure the appropriate distance between the through-via and the castellation, the castellations, and then the side terminals, need to be formed in a lower layer where the distance between the cancellation and the through-via formed in the upper layer does not affect the strength, or in a layer having no through-via. For that reason, the side terminals are much lower than those according to the conventional art. Consequently, when the semiconductor device is mounted on the mounting substrate by soldering, a solder fillet of a sufficient size is not formed between each of the side terminals and the corresponding terminal on the mounting substrate. Thus, disadvantageously, the solder fillets are likely to be broken, degrading reliability.
Furthermore, in order to improve mounting reliability, a method has been disclosed which sets the width of each of the terminals arranged at the opposite ends of a terminal row to be smaller than that of the other terminals. However, also in this case, the reduced height of the side terminals prevents a solder filet of a sufficient size from being formed between each of the side terminals and the corresponding terminal on the mounting substrate. Thus, disadvantageously, the solder fillets are likely to be broken, degrading reliability.